The diagnosis of depression in children and adolescents is both difficult and controversial. This study will compare DSM III criteria in depressed children and adolescents (major depressive disorder and bipolar disorder, phase, versus dsythymic disorder), with biologic tests - the Dexamethasone Suppression Test (DST) and the sleep Polysomnogram. This study will determine whether one or both of these measures in children aged 8 to 18 distinguish between these diagnostic groups and normal controls. In addition, presence of depression will be evaluated using Weinberg criteria (standard and modified). Further, the relationship between symptom severity and each biologic measure, as well as the effects of age and development on each test, will be studied. One hundred and twenty inpatients aged 8 to 18 who meet DSM III criteria for depression, will be studied by two independent experienced clinicians. All patients will be evaluated for other disorders by DSM III as well. Forty will be Tanner Stage 1, 40 Tanner Stage 2 & 3, and 40 Tanner Stage 4 & 5. Within each Tanner group, half (n = 20) will meet DSM III criteria for major depression (unipolar type or bipolar depressed), whereas one half will meet criteria for dysthymia. Each patient will have three nights of sleep polysomnography followed by the DST. A normal control group (n = 60) with approximately 20 in each of the aforementioned developmental groups, who are free of symptoms of depression and other psychopathology, and who are without a family history of affective or other major disorders in first degree relatives, will be evaluated using sleep EEG and the DST to develop normal control values for these age groups.